<!DOCTYPE html>
<html lang="zh_CN">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <script type="text/javascript">
        window.onload = function(){
            var a = document.getElementById("123");
            a.onblur = function(){
                console.log("动态的onblur事件");
                // console代表控制台，log代表打印输出
            }
        }
    </script>
</head>
<body>
    用户密码：<input type="password" id="123">
</body>
</html>